Combined grading and corona shield



Mmh 29, 1960 KAWNS R ETAL 2,930,839

COMBINED GRADING AND CORONA SHIELD Filed March 29. 1955 [17 rayfbrs Jose n Yam/05M,

United States Paten i COMBINED GRADING AND CORONA SHIELD Joseph Kaminski, Jr., and Robert L. McCoy, Baltimore,

Md., assignors to General Electric Company, a corporation of New York Application March 29, 1955, Serial No. 497,569

5 Claims. (Cl. 174-144) This invention relates to a combined grading and corona shield, and more particularly, to a combined grading and corona shield for use in suspended high voltage transmission lines or conductors to provide flashover protection and improved voltage distribution on the suspension insulator string and to suppress corona on articles of line or conductor hardware used to connect the transmission line or conductor to the suspension insulator string.

In the prior art many forms of combined grading and corona shields are provided which do an adequate job. However, many of the prior art formsof combined grading and corona shields tend to be rather complicated and expensive in that they utilize a comparatively large number of separate pieces in their fabrication, and some of said pieces require special bending or the like. Also, some of these prior art forms of combined grading and corona shields have the disadvantage of not being readily assembled or disassembled with respect to the transmission line or conductor, line or conductor hardware, and suspension insulator string without obstruction from said last-mentioned parts. For instance, the construction of the combined grading and corona shield may be such' whereby the transmission line or conductor can be connected to the suspension insulator string and tensioned only by first connecting the shield with respect to the insulator string and then threading the transmission line or conductor through the shield. Likewise, said constructionmay be of such nature whereby the combined grading and corona shield cannot be removed without breaking the connection between the tensioned transmission line or conductor and the insulator string.

Accordingly, it is an object of this invention to provide an improved and more economical combined grading and corona shield which will overcome the above-mentioned disadvantages of the above-discussed prior art forms of combined grading and corona shields.

Our invention comprises a combined grading and coronashield comprising a pair of continuouselongated metallic members having exterior cylindrical surfaces opposite to each other with their respective opposite ends spaced from each other, another continuous elongated metallic member having exterior cylindrical surfaces bent into a generally semi-circular configuration and connected at its opposite ends to central portions of ,said pair of members and another pair of continuous metallic elon gated members connected at one of their ends to said another member adjacent the opposite ends thereof and extending at their other ends towards but short of eac other.

The features of our invention which we believe to be novel are set forth with particularity in the appended claims. Our invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing.

In the drawing, Fig. 1 is an elevation view of a preferred form of our invention. Fig. 2 is an elevation view identical to that of Fig. 1 but being somewhat enlarged and partially broken away. Fig. 3 is a top view of our preferred form of invention. Fig. 4 is an end view of our preferred form of invention viewed from the lefthand side of Fig. 2. Like reference numerals will be used throughout Figs. 1-4 to indicate identical parts.

Referring now to the drawing, and more particularly to Figs. 1 and 2, illustrated therein is a high voltage suspension electrical insulator string 1 suspended at the upper end thereof from a not shown tower structure or the like. The insnlatorstring 1 comprises a plurality of eye bolt and clevis or ball bolt and socket type suspension electrical insulators which are joined together in a string in a manner well known in the art. string 1 is generally vertically disposed, and a generally horizontally disposed electrical transmission line or conductor 2 is connected to and supported from the lower end of the insulator string 1 by virtue of line or con ductor hardware comprising a connector member 3 and a cable clamp 4. The cable clamp 4 is a generally horizontally disposed elongated metal saddle type suspension cable clamp well known in prior art. The cable clamp 4 in a manner well known in the art. In our invention we provide a combined grading and corona shield 5 which can be assembled with respect to the insulator string 1, line hardware 3 and 4, and line or' cable 2 without interference or obstruction therefrom, That is, all the parts 1 to 4 can be interconnected and tensioned as illustrated, and then the corona'shield 5 can be mounted with respect to said tensioned parts without obstruction therefrom. Similarly, the shield 5 can be removed with respect to said assembled parts 1 to 4 without breaking the connection therebetween. Our

combined grading and corona shield 5 will now be described by reference to Figs. 3 and 4 as well as Figs. 1' and 2.

The shield 5 comprises a pair of continuonsi'rod-like metallic members 6 having circular cross sections and smooth outer surfaces. The members 6 may be solid throughout, but preferably are hollow or tubular in order to conserve metal and reduce costs. Each of the cylindrical tubes 6 is bent into an arc-like configuration, and

tubes 6 are spaced with respect to each other whereby the concave outline or surfaces ofthe arc-like membersor tubes 6 face each other. The tubes 6 are disposed ver' tically between the horizontally disposed cable 2 and the lowermost electrical insulator of the string 1 in generally spaced embracing relationship with respect to the lower electrical insulator of the string 1. By viewing Fig. 4

it will be noted that both of the tubes 6 are slightly. tilted toward each other whereby the tubes 6'are gen'-' erally disposed in planes which intersect each other at an obtuse angle alonga line which is disposedhgenerally coincidental with the axis of the cable 2. The opposite respectiveen ds of the pair of strips 6 have hemispherical or rounded closed ends 7 whichare spaced with respect to each other, and the strips 6 are symmetrically or equi- 1 distantly disposed in spaced relationship with respect to the parts 1-4 and their axes.

The reason for tilting the members 6 with respect to each other at an obtuse angle is to ensure that the rounded ends 7 thereof are directed towards and disposed adjacent the line or conductor 2 in closely spaced relation-1;, ship. Inasmuch as the members 6 are at the same elec-' trical potential as conductor 2 in order to suppress" Patented Mar. 29, 1960 The insulator corona at the ends 7 it is necessary to direct the ends 7 towards the conductor 2. if the members 6 were both disposed in an identical horizontal plane the ends 7 would be spaced too far above the conductor 2 and corona would appear at the ends 7 since they would be out of the electrical field or the conductor 2.

The combined grading and corona shield also comprises another continuous rod-lilre metallic member 8 having a circular cross-section and outer surfaces. The member 8 like the members 6 may be solid throughout but preferably is hollow or tubular in order to conserve material and reduce costs. The cylindrical tube 8 is bent into a generally semi-circular or curved U-shaped configuration, and is attached by Welding or the like to the central portions of the pair of tubes 6. Tube 3 extends along the opposite sides of the cable clamp 4 as well as beneath the clamp 4, and is disposed in a plane which is disposed substantially perpendicular to the planes of the pair of tubes 6 and the line or cable 2. That is tube 8 is disposed outside of the obtuse angle defined by the intersecting planes of the tubes 6, and is symmetrically and equi-distantly disposed in spaced relationship with respect to parts 1- The shield 5 is mounted with respect to the parts 1-4 by an attachment fitting comprising a pair of continuous relatively narrow fiat rigid metallic strips or elongated members 9 each connected at their outer ends by welds or the like to the tube or member 8 adjacent to the central portions of the members 6. The support arms 9 are disposed generally within the plane of the member 8 and extend towards but short of each other at their inner ends in spaced relationship to an area disposed generally within the obtuse angle defined by the intersecting planes of the pair of members 6. Each of the inner ends of the support arms 9 has a not shown aperture formed therein. The apertures formed within the inner ends of the support arms 9 are spaced from each other by a distance equal to the distance between a pair of not shown apertures formed in the outer ends of another support arm 10 which is connected at its central portion by welding or the like to the connector 3. The support arm It is also a continuous relatively narrow fiat rigid metallic strip or elongated member, and is disposed generally perpendicularly to the vertically disposed elongated connector 3 and to the axis of the horizontally disposed cable clamp 4' and cable 2.. When the combined grading and corona shield 5 is properly positioned with respect to the parts 1-4 the inner ends of the support arms 9 will make fiat surface engagement with the opposite ends of the support arm it and the apertures formed in the inner ends of the support arms 9 will be aligned with the apertures formed inthe opposite ends of the support arm 16. The support arms 9 can be securely but removably fastened to the support arm 10 by nuts and bolts or the like extending through said aligned apertures. Said nuts and bolts are accessibly located whereby they can be readily worked on with hot line tools.

It will now be seen that our invention provides a very economical combined grading and corona shield which has a very small number of separate pieces whereby the shield is very uncomplicated and easy to manufacture. For instance, the corona and grading shield proper is a unitary structure comprising merely three members 6 and 8. As will be obvious to those skilled in the art, the purpose of members 6 is to provide flashover protection and improved voltage distribution on the suspensioninsulator string 1, and thepurpose of the membe: 8 is .to suppress corona at the sharp edges of the line hardware such as at the sharp edges of the nuts and bolts and the cable seat ends of the cable clamp Additionally, the shield 5 is so configured whereby the shield 5 can be readily assembled or disassembled with respect to the parts1-4 without many obstructions therefrom. For instance, the spaced end of the pair .of members 6 and 9 define an opening therebetween whereby the shield 5 can be readily mounted with respect to the parts 14 after final assembly thereof without the necessity of threading the conductor 2 through the shield 5. Conversely, the shield 5 can be readily removed without breaking any of the interconnections between the parts 1-4 merely by loosening the nut and bolt connections between the arms 9 and 10. With the support arms 9 connected to the shield 5 and the support arm 10 connected to the connector 3, the possible number of falling parts is kept to a minimum depending upon the type of removable fastening means used to connect the inner end of the support arms 9 and the opposite ends of the support arm 10. Furthermore, it will be noted that the various parts of our shield 5 require no complicated bending procedures, and the Welds interconnecting the members 6, 8 and 9 and the nuts and bolts connecting the supporting arms 9 and 10 are so disposed whereby they are adequately shielded against corona emission by the members 6 and 8. Such disposition of said welds and nuts and bolts presents the advantage that the welds do not have to be smoothed and the sharp edges of the nuts and bolts will not cause radio noise.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention, and therefore itis intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A combined corona and grading shield consisting of a pair of continuous metallic cylindrical tubes each bent into an arc-like configuration and disposed opposite to each other with their respective opposite ends spaced from each other, the concave sides of said arc-like configurations facing each other and the planes of said pair of tubes intersecting each other at an obtuse angle, another continuous metallic cylindrical tube bent into a U-shaped configuration having a curved base, the opposite 7 ends of said another tube connected to the central porof a pair of continuous rod-like circular cross sectioned smooth .surfacedmetallic members each bent into an arelike configuration and disposed opposite to each other with their respective opposite ends spaced from each other, said respective opposite ends being rounded, the concave sides of said arc-like configurations facing each other and said pair of members disposed in planes intersecting each other at an obtuse angle, another continuous rod-like circular cross sectioned smooth surfaced metallic member bent into a generally semi-circular configuration and having the opposite ends thereof connected to the central portions of said pair of members by welds, said another member positioned outside said angle and disposed in a plane extending generally perpendicular to the planes of said pair of members, and a pair of continuous elongated metallic members each connected at one of their ends to said another member adjacent said central portions and extending at their other ends towards but short of each other to a position disposed Within said angle, said elongated members disposed substantially Within the plane of said another member and each of said other ends having an aperture therein.

3. A combined corona and grading shield consisting of a pair of continuous hollow tubular circular cross sec tioned smooth surfaced metallic members each bent into an arc-like configuration and disposed opposite to each other with their respective opposite ends spaced from each other, said respective opposite ends closed by generally hemispherically rounded portions, the concave sides of said arc-like configurations facing each other and said pair of members disposed in planes intersecting each other at an obtuse angle, another continuous hollow" tubular circular cross sectioned smooth surfaced metallic member bent into a generally semi-circular configuration and having the opposite ends thereof connected to the central portions of said pair of members by welds, said another member positioned outside said angle and disposed in a plane extending generally perpendicular to the planesof said pair of members, and a pair of continuous relatively narrow flat straight rigid metallic strips each connected at one of their ends by welds to said another member adjacent said central portions and extending at their other ends towards but short of each other in spaced relationship to a position disposed within said angle, said strips disposed substantially within the plane of said another member and each of said other ends having an aperture therein.

4. In a generally vertically disposed suspension electrical insulator string having line hardware at the lower end thereof for supporting a generally horizontally disposed electrical transmission line, a combined grading and corona shield consisting of a pair of continuous elongated metallic members having exterior cylindrical surfaces each bent into an arc-like configuration, said pair of members disposed opposite to each and having their respective opposite ends spaced from each other,

the concave sides of said pair of bent members facing,

each other and said pair of members disposed symmetrically with respect to the axis of said insulator string and the axis of said transmission line and vertically between said transmission line and the lowermost electrical insulator of said insulator string, said respective opposite ends directed towards and disposed adjacent said line, another continuous elongated metallic member having exterior cylindrical surfaces bent into a generally semi-circular configuration, said another member extending around and beneath said transmission line and connected at its opposite ends to the central portions of said pair of members, said another member disposed in a plane extending generally perpendicular to the axis of said transmission line, and another pair of continuous elongated metallic members for supporting said shield from said line hardware, said another pair of members connected at one of their ends to said another member adjacent said central portions and extending at their other ends towards but short of each other, said another pair of members disposed substantially within said plane and removably connected at said other ends to said line hardware.

5. In a generally vertically disposed suspension electrical insulator string having a generally horizontally disposed elongated saddle type conductor clamp supported from the lower end of said insulator string by a generally vertically disposed elongated connector, said clamp having a generally horizontally disposed electrical conductor clamped therein, a combined corona and grading shield consisting of two continuous metallic cylindrical tubes each bent into an arc-like configuration and disposed opposite to each other with their respective opposite ends spaced from each other, the concave sides of said arc-like configurations facing each other, said two tubes disposed vertically between said conductor and the lowermost electrical insulator of said insulator string and within planes which intersect each other at an obtuse angle along a line generally coincidental with said conductor, said two tubes symmetrically and equidistantly spaced with respect to said insulator string, connector, clamp, and conductor, said respective opposite ends directed towards and disposed adjacent said conductor in closely spaced relationship, another continuous cylindrical tube of metal bent into a generally semicircular configuration and connected at its opposite ends to the central portions of said two tubes, said another tube extending around and beneath said clamp in spaced relationship and disposed in a plane extending substantially perpendicular to said conductor, two continuous metallic support arms connected at one of their ends to said another tube adjacent said central portions and extending at their other ends towards but short of each other to a position within said angle, said arms disposed generally within the plane of said another tube, another continuous metallic support arm connected adjacent its central portion to said connector and extending generally perpendicularly of said connector and conductor, and said other ends removably connected to the opposite ends of said another support arm.

References Cited in the file of this patent UNITED STATES PATENTS 1,690,184 Stumm Nov. 6, 1928 2,539,641 Sheadel Jan. 30, 1951 2,597,590 McCoy May 20, 1952 2,741,321 McCoy et a1. Apr. 10, 1956 FOREIGN PATENTS 170,222 Austria Jan. 25, 1952 UNITED STATES PATENT OFFICE- I CERTIFICATE OF CORRECTION- Patent No. 2,930,,839 March 29, 1960 Joseph Kaminski, Jr. et a1.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 9,, after "and" insert smooth Signed and sealed this 13th day of September 1960.

(SEAL) Attest:

KARL AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents UNITED STATES PATENT O-FFICE' CERTIFICATE OF CORRECTION Patent No. 2,930 839 March 29, 1960 Joseph Kaminski, Jr. v et a1.

pears in the printed specification It is hereby certified that error ap and that the said Letters of the above numbered patent requiring correction Patent should readas corrected below.

Column 3 line 9 after "and" insert smooth Signed and sealed this 13th day of September 1960.

(SEAL) Attest: v KARL AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents 

